martin



T. G. MARTIN.

TELEPHONE SYSTEM.

APPLICATION man NOV. 25. 1914. RENEWED AUG. 1. 1918. 1,303,937.

Patented May 20, 1919.

IIMIEMIIH flTTORA/EY UNITED STATES PATENT orrIon TALBOT e. mAnTm, or cnrcneo, ILnmoIs, ASSIGN'OB To .wfoiunnc nLncTnIc comm, or CHICAGO, ILLmoIs, A conronaTIon or ILLINOIS.

Tnmrnom: SYSTEM.

Specification of Letters Patent.

Patented May 20, 1919.

Application flied November 25, 1914, Seria1 No. 874,003. Renewed Augustl, 1918. Serial No. 247,888.

To all whomz't may concern:

Be it known that I, TALBOT G. MARTIA a citizen of the United States of America, and resident of Chicago, Cookcounty, I111- nois, have invented certain new and useful Improvements in Telephone Systems, of which the following is a specification.

My invention relates to automatic and,

semi-automatic telephone systems. ,More particularly my invention relates to telephone systems in which a plurality of trunks are made common for the purpose of extending connections from one point to another. Among the objects of my invention are the following: to provide means for preventing two subscribers calling in onto an auxiliary line, such as an operators head-set at the same time; to provide means for making all of the trunks running to a. par ticular point, such as to a particular operator, busy when a connection is ex-. I gtended to said operator, so as to permit only one call to go to such an operator at -the same time, and to provide means for accomplishing this result over a busy trunk f circuit; to provide means whereby when a subscriber takes a trunk the means for connecting' the other trunks with an auxiliary circuit, such as an operator, will be rendered inoperative; to provide means for preventing interference with release circuits involving busy trunks; to provide means for disconnecting a trunk from the auxiliary circuits when a connection is extended from the trunk; to provide means for restoring the connecting means of idle trunks to normal condition when a connection is extended from a seized trunk and disconnected from the auxiliary circuit; to provide a special form of busy test signaling apparatus which will automatically indicate to the operator whether a call is a reverting call or otherwise; to provide an improved medium of the subscribers individual switch. a

C, cord circuit E and the called subscribers individual switch C to the called sub-Sta tion A. i

The line conductors 10 and 11 of the subscribers substation A terminate in the individual or line switch G. The. line switch,

shown at C is one of a group of similar line switches the plungers (not shown) of which I engage a shaft and are controlled by the operation of the'master switch shown at D in such a manner that they are, when in normal position, held directly infront of is equipped with the necessary apparatus for completing connection with any one ,of a plurality of substations (only one of which is shown) connected to the line conductors 10 and 11 through the line switch C Al-- though there is shown only one substation- A connected to the line conductors 10"{and the terminals of a trunk line leading to an idle cord circuit E. The .cord circuit E' 1 1' it will be understood that a plurality of. like substations may be connected to the said conductors. The ringers of the difierent substations may be arranged in any well known manner to respond to the ringing current generated by some particular one of a plurality of generators.

of any suitable or approved type and comprise the usual receivers 2 and 2, transmitters 3 and. 3, ringers 4: and 4, condensers 5 and 5 andswitch hook springs "7, 8, 9 and 7', 8, 9'. They are connected to the exchange by the conductors 10, 11, and 10, 11, respectively, where the terminate in individual switches C and "respectively, from which normal conductors extend to a plurality of jacks; only. one of which is shown for each line, as J and J, respectively.

The primary switch C is of the general type of line switch shown in British patent to R. W. James, No. 26,301 of 1906, the particular form shown, however, being, similar to that shown in British patent to T. G.

The subscribers substations A and A are i i Martin, No. 1419 of 1910, with the exception that the line relay .and operating magnets are made separate instead of being combined in a single structure. Among other details, the line switch comprises a plunger (not shown) carried upon the end of the plunger arm 12 which is adapted, when the plunger arm is attracted by the magnet 13. to force the plunger into a bank of cont-act springs. forcing the springs 17, 18. 19 and 20 into engagement with the springs 21. 22, 23 and 21 respectively. The magnet 13 also controls the cut-off armature 16. and comprises two windings, namely. the pull-in winding 11 and the cut-off or holding winding 15. The winding 11 is strong enough to operate both the plunger arm 12 and the cutoff armature 16. while the winding 15 is only strong enough to operate the cutoff armature 16 and to hold the plunger arm 12 in an operated position. after it has once been drawn down by the winding 11. The line relay 25 is slow acting. that is. slow to deenergize after its energizing circuit has been broken. so that it may keep the operating winding 11 energized for a short time after the cut-off armature 16 has operated to disconnect said line relay 25 from the line. Although only one set of springs 14 21 inclusive is shown. each line is provided with a plurality of such sets. each set form ing the terminal of a trunk line leading to the cord circuit E. Each trunk line is connected in multiple with the corresponding springs of all the switches of the group which is controlled by the lnaster switch D. The switch C is controlled by the subscriber through the medium of the line relay 25. as will be hereinafter explained. The plungers of the line switch are preferably of the self alining type, that is, they always return to locking engagement with the master switch haft when they become idle.

The master switch D is of the same general type as that disclosed in British Patent No. 26.301 of 1910, referred to above. being. however, of the particular type disclosed in French Patent No. 119.231 of 1912, the circuits however, being slightly modified. Among other details, the master switch D comprises a. starting relay 26. a locking magnet 27 and a restoring magnet 28. As is shown. the usual plunger guide shaft 29, through the medium of which the master switch controls the plungers. is connected with the rotary shaft 29 in such a manner that, as said shaft is rotated back and forth. the plunger guide shaft 29 is oscillated about said shaft 29 as an axis. The shaft 29 is adapted to be rotated in one direction by a spring (not shown) and to be returned against the tension of said spring by a solenoid 30. Secured to the shaft 29 is a cam member 31 provided along its outer edge with notches 32. one for each trunk line to which the line switches have access. The shaft 29" is normally locked against rotation in either direction by the engagement of the lever 33 with one of the notches 32. The lever 33 is controlled by the armature of the relay 2? in such a manner that when said relay is energized. the lever is withdrawn from the cam 31 so as to unlock the shaft 29. The speed of rotation of the shaft 29 and the plunger arm shaft 29 is regulated by means of a suitable governor 34. The spring 35 of the relay 28 is locked in its operated position by the engagement of the spring 35 with the detent. on the side of spring 36. The springs are unlocked by the arm 37 when the shaft 29 has reached the limit of its travel in one direction. The master switch D is also provided with a bank of contacts a. one for each trunk. A wiper t1 keeps the common segment 12 in electrical connection with the individual c011- tacta corresponding to the trunk line before which the idle plungers are resting. In general. the operation of the master switch is as follows: \Vhenever a trunk line is seized by a line switch. the relay 26 is energized which in turn energizes the relay 2? to unlock the shaft 29= through the medium of the double arm and cam 31. a spring (not shown) thereupon rotating the shaft 29 to cause the plunger guide shaft 29 to move the idle plungers away from the trunk just seized and to an idle trunk line. 'hen an idle trunk is reached. the relay 2? deenergizes and again locks the shaft. 'hen the plungers in their operation pass beyond the last trunk line. the arm 38 for es the spring 39 into contact with the spring 10. whereupon the relay 2% energizes and closes the circuit of the solenoid 30. The solenoid. upon energizing rotates the shaft 2 back to its initial position, so as to bring all the plungers which are in engagementwith the plnnger shaft back to a position opposite the first trunk line and to restore the tension of the operating spring. hen the plunger shaft, reaches its initial position. the arm 36 unlocks the spring of relay 28, which permits the solenoid to deenergize and the plunger shaft to come to rest. A relay K is associated with each trunk line leading from the group of line switches to which line C belongs. The re lay K is energized whenever its corresponding trunk is in use. Then all the trunks leading-from' the said group become busy at one time. and therefore all the relays K energize. the relays L and M become. energized over the following circuit: from ground Gr through the contact of springs 92 and 3 of each trunk relay K and through the said relays L and M to battery B. The relay L. upon energizing. removes battery from the pull-in winding of all the line switches of the group, by opening the contact springs 55 and 56. The relay M, upon energizing, opens the circuit of the start relay 26 of the master switch D at the springs 61 and 62, so that the said master switch lays for controlling the same. The relay I isa group, busy relay, that is, it is a relay to make all trunks to an operators position busy as long as'there is an unanswered call at said operators position. The relay I may be common to all the cor-d circuits of an operators position. The meter X is the means for registerin all calls handled by one operator.

The re ays Z, Z and Z furnish means for giving a discriminating busy test whereby the operator can ascertain whether she is testing a multiple jack of the calling line connected to the answering end ofthe cord' or of some other busy line. The keys 7c, I0 I0 7: are the means by which any one of a plurality of generators (only one shown) may be connected to the cord circuit E for signaling purposes. The said keys are so arranged mechanically that when any one of these keys are depressed, any other depressed key will be restored to normal, so as not to allow two generators to be connected to the leads 166 and 167 at the same time. The conductor 200 is multipled through the con tacts of springs 107' and 108 and also 107 and 108 of every cord circuit common toan operators position, the function of which, is

to prevent the connecting of the operators h'eadset P to more than one cord circuit at v the group usying relay I'.- This circuit err-- tends from ground G" through the contactof springs 69 and contact of springs 84:

a time, if it so happened that more than one call was successful in reaching an operators position at one time. y

Having given a (general description of the apparatus involve in the system, in order to give a complete understanding of my invention it will be described how the subscriber at the substation A may obtain connection with the subscriber at substation A. When the receiver at the substation A is removed.

from, the switch hook preparatory to making a call, the engagemehtpf the switch hook springs completes a bridge across the line through the receiver and transmitter-of said hold-in windi This circuit extends from ground Gr 47 and 46, the relay 25 and the conductor 50 to battery B. The relay 25, upon energizing,

operates to closethe circuit through winding 14 of the line switch. C. This circuit extends from ground G through the contact of springs 52 and 53, winding 14, contact of springs 55 and 56, conductor 57, contact of springs 58 and 59 to the battery B. The

windi1'1g 1. upon energizing, attracts the plunger arm 12 (to which is fastened the plun r not shown) and the cut-off armature 16, w ereby the. line conductors 10 and 11 are extended through the contact of the line switch bank sprmgs 17-21 and 2024; the release conductor and trunk-guard conductor are also extended at the same time'by contact of bank springs 18 22 and19-23 respectively to the cord circuit E, and the line relay is disconnected from the line. hen the connectlon is extended to the said cord circuit, the line relay F immeditaely energizes over the followin circuit; from ground G through the win 'ng 66 of relay F, contact of springs 24: and 20, conductor 10 to and through the substation A, return conductor 11, a contact of springs 17 and 21 and the winding 67 of relay F to battery B.

The rela F, upon energizing closes the circuit of t e hold-in winding 15 of the line switch C and the trunk relay K (before the llne relay 25 denergizes) The circuit for G through the win ing of relay H, contact vof springs 74 and 75, contact of springs 22 and 18 and the said winding 15 of line switch Qtobattery B. A guarding ground potentlal 1 s also supplied to the bush 176 of the multiple jack J to make the calling line test busy. The closing of bank springs 19 and 23 4.

causes the master switch D to operate in a well known manner to move the plungers of extends from ground all the line switchesopposite an idle trunk line. A further result of the f energization of the rela F is to close a circuit through i tact' of springs 76 and 75, conductor 79, conductor 89 and relay K to battery B.

The relay K upon energization, closes a circuit which provides a guarding ground potential at the master'switch bank to prevent themaster switch from stopping on this particular trunkline. This circuit extends from ground GE through the contact I of springs 90 and 91 and to master switch bank contact 60. Should the master-switch wiper 41 be rotated over its bank to the contact 60 a circuit would then be closed which extends from master switch bank contact 60, through master-switch wiper 41. bank 12. contacts of springs 61 and (i2 and relay 26 to battery B. As hereinbefore explained the master switch would then be operated. which in turn would move the plungers away from this trunk line so that it could not be selected. In a like manner a guarding ground potential is supplied from ground (i through the contacts of springs 88. 88 etc., upon every trunk line leading to this operators position. The relay H. upon energizing. closes a circuit through the slow act-- ing relay X. This circuit extends from ground G through the contact of springs 103 and 104. springs 95 and 91 and the relay X to battery B. The relay X. upon energizing. closes a circuit through the line signal lamp t and the relay 0. The circuit for the line signal lamp extends from ground G through the springs 10T-109 and 10T'--109 in parallel, springs 71 and T2 and the said lamp to battery B. The circuit for the relay 0 extends from ground G through the springs 109 107 and 109 107 in parallel and the said relay 0 to battery B. The relay 0 upon energizing connects the operator's head set across the line-comluctors of cord circuit E. A further result of the energization of relay X is to disconnect ground from the conductor 200 which multiples through all the other cord circuits of the operator's position. thus making it impossible for the line signal lamp 1 or the relay 0 (which connects the operator's head set to the cord circuit) of any other cird circuit in a certain position to operate.

The disconnection of ground (caused by the energization of relay X) from the conductor 200 which multiples through all cords of one operator's position, prevents more than one sub-station from connecting with the operator's head set. This is accomplished in the following manner: relay N, upon energizing. remains in that condition until the operator plugs into a jack to com plete the call as will be hereinafter explained. It is therefore obvious that there is no ground on springs 10S and 108 which lead to the conductor -200; conductor 200 multiples to corresponding springs 107 and 107 in the remaining cord circuits associated with the operator's posit-ion. Itv is therefore evident that when a. call is directed over any other cord circuit it can proceed as far as and energize its relay X. However there being no ground on the corresponding springslOT and 107 associated with its cord circuit therefore. when the corresponding springs 10?. 109 and 107 and 109 are in contact there is no ground supplied to energize the relay 0. The relay 0 must be energized to complete a. connection through moms? plug P to the bush of jack J, if the line is busy. the relay Z will immediately energize andclose the contact of springs 172 and 173, thus giving the operator a click in the ear. The energizing circuit for relay Z extends from ground upon the bush of jack J through the tip of plug P, springs 160 and 161, springs 100 of relay Q, springs 97 and 96 of relay H. relay Z and the coil Z to battery B. The circuit which is closed to produce the busy click in the operators receiver may be traced from ground G through relay Z contacts of springs 172 and 173 of relay Z. operator's receiver 119, winding 120 of induction coil, springs 117 and 118 of relay 0, and lower winding 170 of relay Y to battery B. The operator immediately informs the calling subscriber that the line is busy or plugs the plug P into a special busy tone jack similar to that shown in the patent to \V. W. Dean. X0. 853.682, issued May 11, 1907. giving the calling subscriber a busy signal. If the substation desired is a su station upon the calling subscriber's line. when the operator touches the plug P to the jack J. the relay Z will actas a buzzer, due to the fact that the said relay short circuits itself at the springs 171 and 175 every time the said relay energizes. The short circuiting ath for relay Z extends from the bush 0? jack J (or one of its multiples) through the bank springs 18 and 22. springs 115 and 116. springs 175 and 174, relay Z, springs 96 and 97. springs 100, springs 161 and 160 and the tip of plug P to the bush of jack J. The buzzing eifect of the relay Z notifies the operator that the substation desired is one upon the calling substat-ions line and she will immediately proceed to complete the connection.

Assuming that the line desired is idle, the operator immediately plugs the plu P into the jack J which causes the relay 5 to immediately energize. This circuit extends from ground G through the said relay, sleeve of plug P bush of jack J, cut-ofi winding 133 of line switch C to battery B. The cut-off winding upon energizing, disconnects the linerelay 140 from the line and completes the connection through to the sub station A. The relay Q. upon energizing, breaks the circuit of relay N at the springs 101 and 103 and closes a circuit through the relay W and the supervisory lamp t at th springs 103 and 102. A further result of v the energization of relay Q is to disconnect the relays Z and Z from the tip strand of.

' the cord circuit E at the springs 100, and

to connect a holding ground to the trunk release conductor 79 through the springs 98 and 99 independent of the springs 71 and 75. The circuit for this additional holding ground extends from ground G through winding of relay H, springs 98 and 99 to release trunk conductor 79. The relay V set from the cord circuit E. The operators previously operated to normal. 85 S position is now in readiness to receive another call.

The operator now presses the key is to connect the generator R to the called line. The key It looks in its depressed position '(holding the contact of springs 146-147 and 142143 closed but allowing the springs 1H and 145 to make contact for an instant and then to separate) and restores the key The relay is energized as soon as key It is depressed and operates to close a locking circuit through the springs 154 and 153 independent of the springs 144 and 145 at the key K. The said locking I circuit extends from ground Gr through the contact of springs 103 and 102, springs 157 and 158. springs 153 and 154 and through the said relay S to battery B. 'A further result of the energization of relay S is to close a circuit through the ringing relay U at the springs 151 and 152. The said ringingrelay circuit extends fromground G" through interrupting device T contacts of springs 152 and 151, through winding of ringing relay U to the battery B. The relay U, upon energizing, disconnect-s the calling line from the called line and bridges the generator R across the called line over the following path: from one terminal of the said generator, springs 113 and 112 of key It, springs 159 and 160, tip of plug P. tip spring 125 of jack J. to and through the substation A. springs 132 and 131, ring spring 126 of jack J, ring of plug P. springs 163 and 162 of relay U, coil V and springs 146 and 147 back to the opposite terminal of generator R. The ringing relay U is energized intermittently, through the medium of interrupter T.- The springs 160 and 161 and springs 163 and 161 of relay U are shunted by a very high resistance or by a very small condenser. This allows a very small portion of the ringingcurrent to be transmitted back through the calling line to the calling substation, thus giving the calling subscriber an audible ringing signal, informing him that the called subscriber is being signaled. I have found that the high resistance may be merely a line drawn by a carbon pencil on the insulating mounting between the said springs or the condenser may be the capacity ellect of a pair of insulated wires twisted together one wire electrically connected to one spring and the other to the other spring. Either method gives very satisfactory results. Upon the response of the called subscriber his line is provided with talkingcurrent through the windings 170 and 171 of the relay Y which is normally bridged across the conductors 137 and 138. The relay Y, upon energizing. opens the circuit of the supervisory lamp t at the springs 155 and 156 and opens the circuit of the relay S at the springs 157 and 15 8. The

cuit of relay U. at the springs 151 and 152. The subscribers may now carry on an uninterrupted conversation over the heavy conductors shown.

The replacing of, the receiver at the called and calling substations signifies to the operator that the conversation has terminated. When the receiver at the substation A is restored to the switch hook, the separation of the hook switch springs 7 and 8 destroys the energizing circuit of the line relay F. The relay F upon dei nergizing, causes the su pervisory lamp t to glow over the following circuit: from "ground G through the springs 103 and 102, springs 7 3 and 72 and the lamp t to battery B. The replacing of the receiver at the called substation A opens the circuit of the relay Y, ,which, .upon del relay S, upon deenergizing. opens the cir- 1 to battery B. The operator receiving the disconnect signal removes the plug P from the jack J. thus breaking the circuit of the relay Q and the cut-off winding 133 of line switch C. The relay Q. upon deenergizing, opens the circuit. of the relay V at the springs 102 and 103,' removes the ground from the holding winding 15 of line switch C at springs 98 and 99, and opens the circuit of the supervisory lamps t and F. The holding winding of the line switch C. upon deenergizing. allows the line switch plunger to be returned to normal. The relay \V is preferably made slow-acting. so that the line switch C is given suflicient time to return to normal before the release conductor 7 9 is again connected to the group busying relay common to the various other cord circuits.

It will, therefore, be seen that I provide a semi-automatic traflic distributer system, in which an operator may be assigned exclusively to take care of the t-raflic over a certain number of trunks. Another operator may be assigned to take care of traflic over another group of trunks, and so on. There may be a plurality of groups of subscribers lines and from each group of lines trunks may run to each operator. For example, in a system in which the so-called Keith units are used. one or more trunks from each unit may be assigned to each operator. Furthermore. it will be seen that I provide means for insuring that no two subscribers will call in on an operator at the same time. When a subscriber calls in on one trunk he energizes the magnet I. This magnet energizes regardless of which trunk is taken. Vhen a subscriber takes a trunk he makes, of course, his own particular trunk busy and by energizing the magnet I he makes all the remaining trunks which are at. the time unseized busy until the operator completes the connection. I do not claim broadly this idea in this case. but I do claim the use of the busy trunk or of the release trunk for making the said non-seized trunks busy.

It. will be seen furthermore that even if two subscribers were to take ofi their receivers at the same instant and were to take trunks simultaneously, the relay X nearest the ground G would cut off the round G? from all of the relays 0 associated with those trunks which are farther from ground G and this makes it impomible for one of the subscribers to cut in on the operators head-set. Obviously, therefore, the provision of the relay I and of the relays X make it absolutely certain that no two subscribers may cut. in on the operators position at the same time.

It will be seen, therefore, that b the provision of the slow-acting relay W it is impossible for any subscriber who is initiating a call and who is holdin the relay I energized to interfere with t e release of some other subscriber who is through talking, because the relay IV prevents the relay I from putting a uarding potential on the trunk release conguctor until. after the connection is restored. In this system it will be seen that I have also provided means for disconnecting a trunk automatically from an auxiliary circuit, such as the operators headset, as soon as the operator extends the connection. Furthermore, the act of the operator extending the connection beyond her position automatically restores the circuit and makes itpossible for any relay 0 to be energized in a new connection.

I have also provided. a new arrangement by means of which the relays Z and Z operate to give a single kick to the operator when she tests a called line, if the called line is not the same one that originated the call.

On the other hand, if it is the one that originated the call, the action of the relay Z is kept up and impulses continue to be repeated to the operator, which indicate to her that the connection is from one party line subscriber to another one on the same line. The relay Z will continue to flutter in this last instance. because through the action of the springs 171 and 175 it short circuits itself to ground via the springs 115 and 116 of relay 0, which is the ground on the release conductor 79, which is holding up the line switch C. It will be seen in this connection that I provide also a supervisory relay Y and that. this relay is normally connected with the plug, whereas the relay Z is normally disconnected from the plug. It will also be seen that I provide a new arrangement for automatically controlling the ring ing current through the medium of the starter relay S in combination with the keys, which starter relay S is provided with a locking circuit under the control of the relay Y. It will also be seen that I provide a new arrangement by means of which the ringer relay U not only rings the called subscriber, but also notifies the calling subscriber that ringing current is being supplied to the called line. Also I provide a new arrange ment by means of which the relays Q and N directly control the operation of the meter magnet.

'hat I. claim as my invention is:-

1. In a telephone system, a plurality of trunks each comprising a main circuit and a busy test circuit, means including a plurality of progressively movable trunking switches controlled by a common master switch mechanism, for seizing any one of said trunks and means operable when a trunk is seized for making every other idle trunk busy when the seizure is made, means for releasing the connection comprising a release circuit associated with each trunk, and

means for opening the release circuit to initiate the release, said busy test and release circuits having sections in common.

2. In a telephone system, a plurality of trunks each comprising a main circuit and a busy test circuit, means for seizing any one of said trunks and means operable when a trunk is seized for making every other idle trunk busy when the seizure is made, means for releasing the connection comprising a release circuit associated with each trunk closed during conversation, means for opening the release circuit to initiate the release, said busy test and release circuits having sections in common, and means for extending the main circuit and for rendering the said other trunks non-busy when the circuit is extended.

3. In a telephone system, a. plurality of trunks each comprising a main circuit and a busy test circuit, means including a plurality of progressively movable trunking switches controlled by" a common master opening said release circuit to initiate the release, said busy test circuit and release circuit having sections in common; another group of trunks each comprising a main circuit and a busy test circuit, means for seizing any one of the trunks of the second group, and means operable when a trunk is seized for making every other trunk in both groups busy if idle when the said seizure is made.

4. In a telephone system, a plurality of trunks each comprising a main circuit and a busy test circuit, means including a plurality of progressively movable trunking switches controlled by a common master switch mechanism for seizing any one of said trunks, means for releasing the connection comprising a release circuit, said busy test circuit and release circuit having sections in common; another group of trunks each comprising a main circuit and a busy test circuit, means for seizing any one of the trunks of the second group, means for releasing the connect-ion comprising'a release circuit, means for opening said release circuit to initiate the release, said last busy test circuit and said last release circuit having sections in common, and means operable when a trunk is seized for making every other trunk in both groups busy if idle when the said seizure is made.

5. In a telephone system, a-plurality of trunks each comprising a main circuit and a busy test circuit, means including a. plura'lity of progressively movable trunking switches controlled by a common master switch mechanism for seizing any one of said trunks, means for releasin the connection comprising a.,release circuit, means for opening said release circuit to initiate the release, said busy test circuit and release trunks of the secondgroup, means for rcleasing the connection comprising a release circuit closed during conversatlon, means for opening said release circuit to initiate the release, said last busy test circuit and said its release conductor when circuit having sections in common; aiiother grou of. trunks 'each comprising a main circuit and a busy test 'circuit,-means for seizing any one of the trunks ofthe second group, means operable whena trunk is seized for'inakin every other trunk in both groups busy if i le when the said seizure is made, and means for extendi the main cir-- cuit and for rendering the sai other trunks non-busy when the circuit is-extended.

3. In a telephone system,"a plurality of trunks each comprisinga main circuit and a busy test circuit, means for seizing any one of said trunks, means for releasing the con-' nection comprising a release circuit, said busy test circuit and release circuit having sections in common; another group of trunks each comprising a main circuit and a busy last release circuit having sections in common, means operable when a trunk is seized for making every other trunk in both groups busy if idle when the said seizure is made, and means for extending the main circuit and for rendering the said other trunks nonbusy when the circuit is extended.

7. In a telephone system, a plurality of,

trunks each comprising a talking circuit and a release conductor associated therewith,

means for establishing connection with any one of said trunks, release apparatus for breaking the connection, a release circuit.

closed during conversation comprising the release conductor associated with the connected trunk for controlling said release-tap paratus, means for opening said release circuit to initiate the release, means for making any trunk busy when seized comprising the release conductor, and means operable when any trunk is seized for making every other trunk, idle at the "time of seizure, busy via the seizure is made. Y

8. In a telephone system, a plurality of trunks each comprising a talkin circuit and a release conductor associate therewith, means for establishing connection with any one of said trunks, release apparatus for breaking the connection, a release circuit closed during conversation comprising the release conductor associated with the .connected trunk for controlling said release apparatus,-means for opening said release circuit to initiate the release, means. for makmg any trunk busy when seized comprising the release conductor; another group of trunks each comprising a main talking circuit, means for establishing connection with any one of the trunks of said second group, release apparatus for breaking said connection in'the second group, a release circuit comprising a conductor associated with the connected trunk and means for making any trunk of the second group busy when seized comprising its release conductor, and means,

1 9. In a telephone system, a plurality of one of said trunks, release'apparatus for breaking the connection, arelease circuit closed during conversation comprising the release conductor associated with the con-' I p nectedtrunkfor controlling said release aptest c rcuit, means for seizmg any oneiofi-themfcuit to initiate the release. means for making any trunk busy when seized comprising the release conductor. means operable when any trunk is seized for making every other trunk. idle atthe time of seizure. busy via its release conductor when the seizure is made. and means for extending the main circuit and for rendering the said other trunks nonbusy when the circuit is extended.

10. In a telephone system. a plurality of trunks each comprising a talking circuit and a release conductor associated therewith, means for establishing connection with any one of said trunks. release apparatus for breaking the connection. a release circuit closed during conversation comprising the release conductor associated with the connected trunk for controlling said release apparatus. means for opening said release circuit to initiate the release. means for making any trunk bus) when seized comprising the release conductor; another group of trunks each comprising a main talking circuit. means for establishing connection with any one of the trunks of said second group. release apparatus for breaking said connection in the second group. a release'circuit comprising a conductor as ociated with the connected trunk and means for making any trunk of the second group busy when seized comprising its release conductor. means operable when any trunk is seized for making every other trunk in both groups. idlev at the tim of seizure. busy via its release conductor when the seizure is made. and means for extending the lnain circuit and for rendering the said other trunks non-busy when the circuit is extended.

11. In a telephone system. a plurality of trunks each comprising a main circuit and a busy test circuit. means including a plurality of progressively movable trunking switches controlled by a common master switch mechanism for seizing any one of said trunks and electromagnetic means operable when a trunk is seized for making every other idle trunk busy when the seizure is made, and means for releasing the connection comprising a release circuit associated with each trunk, means for opening said release circuit to initiate the release. said busy testand release circuits having sections in common.

12. In a telephone system, a plurality of trunks each comprising a main circuit and a busy test circuit. means including a plurality of progressively movable trunking switches controlled by a common master switch mechanism for seizing any one of said trunks and electromagnetic means operable when a trunk is seized for making every other idle trunk busy when the seizure, is made. means for releasing the connection comprising a release circuit associated with each trunk, means for opening said release circuit to initiate the release. said busy test and release circuits having. sections in common. and means for extending the main circuit and for rendering the said other trunks non-busy when the circuit is extended.

13. In a telephone system. a plurality of trunks each comprising a main circuit and a busy te t circuit. means for seizing any one of said trunks. means for releasing the connection comprising a release circuit closed during conversation. means for opening said release circuit to initiate the release. said busy test circuit. and release circuit having sections in common: another group of trunks each comprising a main circuit and a busy test circuit. means for aizing any one of the trunks of the second group. and electromagnetic means operable when a trunk is seized for making every other trunk in both groups busy if idle when the said seizure is made.

14. In a telephone system, a plurality of trunks each comprising a main circuit and a busy test circuit. means for seizing any one of said trunks. means for leleasing the connection comprising a release circuit. said busy test circuitand release circuit having sections in common; another group of trunks each comprising a main circuit and a busy test circuit. means for seizing any one of the trunks of the second. group, means for releasing the connection comprising a release circuitclosed during conversation. means for opening said release circuit to initiate the release. said last busy test circuit and said last. release circuit having sections in common. and electromagnetic means operable when a trunk is seized for making every other trunk in bot-h groups busy if idle when the said seizure is made.

15. In a telephone system, a plurality of trunks each comprising 'a main circuit and a busy test circuit, means including a plurality of progressively movable trunking switches controlled by a common master switch mechanism for seizing any one of said trunks. means for releasin the connection comprising a release circuit, means for opening said release circuit to initiate the release. said busy test circuit and release circuit having sections in common; another group of trunks each comprising a main circuit and a busy test circmt, means for seizing any one of the trunks of the second group, electromagnetic means operable when a trunk is seized for making every other trunk in both groups busy if idle when the said seizure is made, and means for extending the main circuit and for renderin the said other trunks non-busy when the circuit is extended.

16. In a telephone system, a plurality of trunks each comprising'a main circuit and a busy test circuit. means including a plu rality of progressively movable trunking switches controlled by a common master switch mechanism for seizing. any one of said trunks, means for releasing the connection comprising a release circuit, said busy test circuit and release circuit having sec- *tlOIlS in common; another group of trunks and means for extending the main circuit and for rendering the said other trunks non-busy when the circuit is extended.

17. In' a telephone system, a plurality of trunks each comprising a talking circuit and a release conductor associated therewith, means for establishing connection with any one of said trunks, release apparatus for breaking the connection, a release circuit closed during conversation comprising the release" conductor associated with the connected trunk for controlling said release apparatus, means for opening said release cir cult to initiate the release, means for makmg any trunk busy when seized comprising the release conductor, and electromagnetic means operable when any trunk is seized for making every other trunk, idle at the time of seizure, busy via its release conductor when the seizure is made.

18. In a telephone system, a plurality of trunks each comprising a talking circuit and a release conductor associated therewith, means for establishing connection with any one of said trunks, release apparatus for breaking the connection, a release circuit closed during conversation comprising the release conductor associated .with the connected trunk for controlling said release apparatus. means for opening said release circuit to initiate the release, means for making any trunk busy when seized comprising the release conductor; another group of trunks each comprising a main talking circuit, means for establishing connection with any one of the trunks of said second group, release apparatus for breaking said connection in the second comprising a conductorassociated with the connected trunk and means for making any trunk of the second group busy when seized comprising its release conductor, and electromagnetic means operable when any trunk is seized for making every other trunk in both groups, idle at the time of seizure, busy viadits release conductor when the seizure is ma e.

19. In a telephone system, a plurality of electromagnetic group, a release circuit trunks each comprising a talking circuit, and a release conductor associated therewith, means for establishing connection with any one of said trunks, release apparatus for breaking the connection, a release circuit closed during conversation comprising the release conductor associated with the connected trunk for controlling said release apparatus, means for opening said release circuit to initiate the release, means for making any trunk busy when seized comprising the release conductor, electromagnetic means operable when any trunk is seized for making every other trunk, idle at the time of seizure, busy via its release conductor when the seizure is made, and means for extending the main circuit and for rendering the said other trunks non -busy when the circuit is extended.

20. In a telephone system, a plurality of trunks each comprising a talking circuit and a release conductor associated therewith, means for establishing connection with any one of said trunks, release apparatus for breaking the connection, a release circuit closed during conversation comprising the release conductor associated with the connected trunk for controlling said release apparatus, means for opening said release circuit to initiate the release, means for making any trunk busy when seized comprising the release conductor; another group of trunks each comprising a main talking circuit, means for establishing connection with any one of the trunks of said second group, release apparatus for breaking said connection in the second group, a release circuit com prising a conductor associated with the con' nected trunk and means for making any trunk of the second group busy when seized comprising its release conductor, electromagnetic means operable whenany trunk is seized for making every other. trunk in both groups, idle at the time of seizure, busy via its release conductor when the seizure is made, and means for extending the main circuit and for rendering said other trunks non-busy when the circuit is extended.

21. In a telephone system, a plurality of trunks each comprising a main circuit and a busy test circuit, means including a. plurality of progressively movable trunln'ng switches controlled by a common master switch mechanism for seizing any one of said trunks and for making the seized trunk busy, means opera-ble when a trunk is seized for making every other trunk busy, when the seizure is made, via their busy test circuits, means for releasing the seized trunk comprising a release circuit passing over the busy test circuit, and means for opening said release circuit to initiate the release.

22. In a telephone system, a plurality of lines, a common battery, means for sending current from said battery over Said lines,

' lishment of current in the calling line. means for releasing the seized trunk comprising a release clrcult passmg over the busy test clrcult, and means for opemng said release circuit to initiate the release.

:23. In a telephone system, a plurality of trunks each comprising a main circuit and a busy test circuit, automatic means including a plurality of progressively movable trunking switches cont-rolled by a common master switch mechanism for seizing any one of said trunks and for making the seized trunk busy. automatic means operable when a trunk is seized for making every other trunk busy, when the seizure is made, via their busy test circuits, automatic means for releasing the seized trunk comprising a release circuit passing over the busy test circuit, and means for opening said release circuit to initiate the release.

2-1. In a telephone system, a plurality of lines, a'common battery, means for sending current from said battery over said lines, a plurality of trunks each comprising a main circuit and a busy test circuit, automatic means for seizing any one of said trlmks for one of said lines to form an extended talking circuit of the calling line and the said main circuit, automatic means for making said seized trunk busy, means operable when a trunk is seized for making every other trunk busy as a result, via their busy test circuits, all as a result of the firstestablishment of current in the calling line, automatic means for releasing the seized trunk comprising a release circuit closed during conversation passing over the busy test circuit, and means for opening said release circuit to initiate the release.

25. In a telephone system, a plurality of trunks each comprising a main circuit and a busy test circuit, means including a plurality of progressively movable trunking switches controlled by a common master switch mechanism for seizing any one of said trunks and for making the seized trunk busy; another group of trunks each comprising a main circuit and a busy test circuit, means for seizing any one of the trunks in said second group and for making the trunk busy when seized; means operable when a trunk is seized for making every other trunk in eitheragroup busy when a seizure is made Via their busy test circuits, means for releasing the seized trunk comprising a release circuit passing over the busy test circuit. and means for opening said release circuit to initiate the release.

26. In a telephone system, a plurality of trunks each comprising a main circuit and a busy test circuit, means including a plurality of progressively movable trunking switches controlled by a common. master switch mechanism for seizing any one of said trunks and for making the seized trunk busy; another group of trunks each comprising a main circuit and a busy test circuit, means for seizing any one of the trunks in said second group and for making the trunk busy when seized; means operable when a trunk is seized for making every other trlmk in either group busy when a seizure is made via their, busy test circuits, means for releasing the seized trunk comprising a release circuit passing over the busy test circuit, means for opening said release circuit to initiate the release, and means for extending the main circuit and for rendering the said other trunks non-busy when the circuit is extended.

27. In a. telephone system, a plurality of trunks each comprising a main circuit and a busy test circuit, automatic means including a plurality of progressively movable trunking switches controlled by a common master switch mechanism for seizing any one of said trunks and for making the seized trunk bus another group of trunks each comprising a main circuit and a busy test circuit, automatic means for seizing any one of the trunks in said second group and for making the trunk busy when seized; automatic means operable when a trunk is seized for making every other trunk in either group busy when a seizure is made via their busy test circuits, automatic means for releasing the seized trunk comprising a release circult passing over the busy test circuits, and means for opening said release circuit to initiate the release.

28. In a telephone system, a plurality of trunks each comprising a main circuit and a busy test circuit, an auxiliary circuit and connecting means for each trunk for connecting the trunk with the auxiliary circuit, means for seizing any one of said trunks and for making the seized trunk busy, means operable when :a trunk is seized for making every other idle trunk busy as a result of the seizure, means for operating the said connecting means of the seized trunk to connect the seized trunk to the auxiliary circuit, and means for making the connecting means of the other trunks inoperativ 29. In a telephone system, a plurality of trunks each comprising a main circuit and a busy test circuit, an auxiliary circuit and connecting means for each trunk for connecting the trunk with the auxiliary circuit, means for seizing any one of said trunks and for making the seized trunk busy, means operable when a trunk is seized for making every other idle trunk busy as a result ofthe seizure, means for operating the said connecting means of the seized trunk to connect the seized trunk to the auxiliary circuit, means for making the connecting means of the other trunks inoperative, and means for releasing the seized trunk comprising a release circuit passing over the busy test circuit.

30. In a telephone system, a plurality of trunks each comprising a main circuit and a busy test circuit, an auxiliary circuitand connecting means for each trunk for connecting the trunk with the auxiliary circuit, means for seizing any one of said trunks and for making the seized trunk busy, means operable when a trunk is seized for making every other idle trunk busy as a result of the seizure, means for operating the said connecting means of the seized trunk to connect the seized trunk to the auxiliary circuit, means for making the connecting means of the other trunks inoperative, and means for extending the main circuit and for rendering the said other trunks non-busy when the circuit is extended.

31. In a telephone system, a plurality of trunks each comprising a. main circuit and a busy test circuit, an auxiliary circuit and connecting means for each trunk for connecting the trunk with the auxiliary circuit, means for seizing any one of said trunks and for making the seized trunk busy, means operable when a trunk is seized for making every other idle trunk busy as a result of the seizure, means for operating the said connecting means of the seized trunk to connect the seized trunk tothe auxiliary circuit, means for making the connecting means of the other trunks inoperative, means for releasing the seized trunk comprising a release circuit passing over the busy test circuit, and means for extending the main circuit and for rendering the said other trunks non-busy when the circuit is extended.

32. In a telephone system, a plurality of trunks, means for seizin any on of said trunks, means for exten ing a connection from the seized trunk to an operators head set, and means controlled from the seized trunk for preventi the maintenance of an extension from anot ier one of said trunks to said operators head set, said last means also cont-rolled from the seized trunk to automatically extend a connection from the other trunk.

33. In a telephone system, a plurality of trunks, means for seizing any one of Said trunks, means for extending a connection from the seized trunk to an operators head set, and means controlled from the seized trunk for rendering inoperative the said second means associated with another trunk, said last means also controlled from the seized trunk to automatically extend a con.

nection from the other trunk.

34. In a telephone system, a plurality of trunks, means for 'seizin any one of said from the seized trunk to an operators head set, and electromagneticmeans controlled from the seized trunk for rendering inoperative the said second means associated with another trunk, said last means also controlled from the seized trunk to automatically extend a connection from the other trunk.

36. In a telephone system, a plurality of trunks, means for seizing any one of said trunks, means for extending a connection from :the seized trunk to an operators head set, and means controlled from the seized trunk for renderin inoperative the said second means of anotlier trunk to prevent two connect-ions existing at the same time from two separate trunks to the operators head set, said last means also controlled from the seized trunk to automatically extend a connection from the other trunk.

37. In a telephone system, a plurality of trunks, means for seizin any one of said trunks, means for exten ing a connection from the seized trunk to an operators head set, means controlled from the seized trunk for rendering inoperative the said second means of another trunk to prevent tsvo connections existing at the same tune from two separate trunks to the operators head set, and means under the control of the operator for extendingconnection from the seized trunk and for then restoring said second means to operative condition, said last means also controlled from the seized trunk to automatically extend a connection from the other trunk.

38. In a telephone system, a plurality of trunks, automatic means for seizing any one of said trunks, means for extending a connection from the seized trunk to an operators head set, and means controlled from the seized trunk for rendering inoperative the said second means of anot-her trunk to prevent two connections existing at the same time from two separate trunks to the operator's head set, said last means also controlled from the seized trunk to automatically extend a connection from the other trunk.

39. In a telephone system, a plurality of trunks, means for seizing any one of said trunks. means for extending a connection from the seized trunks to an operator's head set, and automatic means controlled from the seized trunk for rendering inoperative the said second means of another trunk to prevent two connections existing at the same time from two separate trunks to the operators head set. said last means also controlled from the seized trunk to automatically extend a connection from the other trunk.

10. In a telephone system. a plurality of trunks. automatic means for seizing any one of said trunks. means for extending a connection from the seized trunk to an operator's head set. and automatic means controlled from the seized trunk for rendering inoperative the said second means of another trunk to prevent two connections existing at the same time from two separate trunks to the operators head set, said last means also controlled from the seized trunk to automatically extend a connection from the other trunk.

41. In a telephone system, a plurality of trunks, automatic means for seizing any one of said trunks, means for extending a connection from the seized trunk to an operator's head set, means controlled from the seized trunk for rendering inoperative the said second means of. another trunk to prevent two connections existing at the same time from two separate trunks to the operators head set, and means under the control of the operator for extending connection from the seized trunk and for then restoring said second means to operative condition, said last means also controlled from the seized trunk to automaticlly extend a connection from the other trunk.

42. In a. telephone system, a plurality of trunks, means for seizing any one of said trunks. means for extending a connection from the seized trunk to an operators head set, automatic means controlled from the seized trunk for rendering inoperative the said second means of another trunk to prevent two connections existing at the same time from two separate trunks to the operators head set, and means under the control of the operator for extending connection from the seized trunk and for then restoring said second means to operative condition, said last means also controlled from the seized trunk to automatically extend a connection from the other trunk.

43. In a telephone system, a plurality of trunks, automatic means for seizing any one of said trunks, means for extending a connection from the seized trunks to an operator's head set. automatic means controlled from the seized trunk for rendering inoperative the said second means of another trunk to prevent two connections existing at the same time from two separate trunks to the operator's head set, and means under the control of the operator for extending connection from the seized trunk and for then restoring said second means to operative condition. said last means also controlled from the seized trunk to automatically extend a connection from the other trunk.

44. In a telephone system, a line, a trunk normally disconnected from said line, an operator's head set normally disconnected from said trunk, a progressively movable switch for establishing connection with said trunk line, and a non-progiessively movable switch for then connecting said trunk line with said operator's head set, said last means also controlled from the seized trunk to automatically extend a connection from the other trunk.

' 45. In a telephone system, a plurality of lines. a conunon battery, means for sending current from said battery over said lines, aplnrality of trunks accessible to said lilies,

' an operators head set. and an operator's po sition, means for connecting a trunk with the operators head set and means for connecting another trunk with the operator's head set. means for connecting one of said lines with-one of said trunks whereby it may then be connected wit-h said operators head set responsive to the first establishment of current. in the calling line, and means for rendering the other head set connecting means inoperative, lines extending from the operators position, and operator controlled means for extending connection from the calling line to one of said last named lines and for then rendering operative the said means previously rendered inoperative, said last means also controlled from the seized trunk to automatically extend aconnection fron the other trunk.

t6. In a telephone system. a plurality of trunks. automatic means for seizing any one of said trunks, means for extending a connection from the seized trunk to an ope-ra'tors head set, and automatic means controlled from the seized trunk for preventing the maintenance of an extension from another one of said trunks to said operator's head set, said last means also controlled from the seized trunk to automatically extend a connection from the other trunk.

47. In a. telephone system, a plurality of trunks, automatic means for seizing any one of said trunks, means for extending a connection from the seized trunk to an operators head set, and automatic means controlled from the seized trunk for rendering inoperative the said second means associated wit-h another trunk, said last means also controlled from the seized trunk to auto matically extend a connection from the other trunk.

48. In a telephone system, a plurality of trunks each comprising a main circuit and a busy test circuit, means for seizing any one of said trunks and for making the seized trunk busy, means operable when a trunk is seized for applying a busy potential to every other idle trunk n'a their busy test circuits to make the idle trunks busy, means for preventing the said last potential applying means from applying a potential to the busy test. circuit of any trunk that is busy at the time of said seizure, and means for releasing said last mentioned busy trunk comprising release circuits passing over -the busv test circuits of said last busy trunks.

In a telephone system, a plurality of trunks each comprising a main circuit and a.

' busy test circuit, means for seizing any one of said trunks and for making the seized trunk busy, means operable when a trunk is seized for applying a busy potential to every other idle trunk via their busy test circuits to make the idle trunks busy, means for preventing the. said last. potential applying means from applying a potential to the busy test circuit of any trunk that is busy at the time of said seizure, means for releasing said last mentioned busy trunks comprising release circuits passing over the busy test circuits of said last busy trunks and means for extending the main circult and tor rendera ing the said other trunks non-busy when the circuit is extended.

'50. In a telephone system, apliunlit-y of trunks each comprising a main circuit and a busy test circuit, automatic means for seizing any one of said trunks and for making the seized trunk busy. automatic means operable when a trunk is seized for applying a busy potential to every other idle trunk via their busy test circuits to make the idle trunks busy, automatic means for preventing the said last potential applying means from applying a potential to the busy test circuit of any trunk that is busy at the time of said seizure, and means for releasing the seized trunk and other busy trunk comprising release circuits passing over the busy test circuits of the seized trunks.

51. In a telephone system. a plurality of trunks each com-prising a main circuit and a busv test circuit. automatic means for seizing any one of said trunks and for making the seized trunk busy, automatic means operable when a trunk is seized for applying a busy potential to every other idle trunk via their busy testcircuits to make the idle trunks busy. automatic means for preventing the. said last potential applying means from applying a potential to the busy test circuit of any trunk that is busy at the time of said seizure, automatic means for releasing said last mentioned busy trunks comprising release circuits paming over the busy test circuits of said last busy trunk-and manual means for extending the main circuit and for rendering the said other now busy trunks non-busy when the circuit is extended.

52. In a telephone system, a plurality of trunks each comprising a main circuit and a busy test circuit, an auxiliary circuit and connecting means for each trunk for connecting the trunk with the auxiliary circuit, automatic means for seizing any one of said trunks and for making the seized trunk busy, automatic means operable when a trunk is seized for making every other idle trunk busy as a result of the seizure, automatic means for operating the said connecting means of the seized trunk to connect the seized trunk to the auxiliary circuit, automatic means for making the connecting means of the other trunks inoperative, and automatic means for releasing the seized trunk comprising a release circuit passing over the busy test circuit.

53. In a telephone system, a plurality of trunks each com-prising a main circuit and a busy test circult, an auxiliary circuit and connecting means for each trunk for con necting the trunk with the auxiliary circuit, automatic meansfor seizing any one of said trunks and for making the seized trunk busy, automatic means operable when a trunk is seized for maln'ng every other idle trunk busy as a result of the seizure, automatic means for operating the said'connecting means of the seized trunk to connect the seized trunk to the auxiliary circuit, automatic means for making the connecting means of the other trunks inoperative, and manual means for extending the main circuit and for rendering the said other trunks non-busy when the circuit is extended.

54. In a telephone system, a plurality of trunks each comprising a main circuit and a busy test circuit, an auxiliary circuit and connecting means for each trunk for connecting the trunk with the auxiliary circuit, automatic means for seizing any one of said trunks and for making the seized trunk busy, automatic means operable when a trunk is seized for making every other idle trunk busy as a result of the seizure, automatic nteans for operating the said connecting means of the seized trunk to connect the seized trunk to the auxiliary circuit, automatic means for making the connecting means of the other trunks inoperative, automatic means for releasing the seized trunk comprising a release circuit passing over the busy test circuit, and manual means for ex-.

tending the main circuit and for rendering the first said idle trunks non-busy when the circuit is extended.

55. In a telephone system, a plurality of trunks each comprising a main circuitand a busy test circuit. means for seizing any one of said. trunks and for making the seized trunk busy. means operable when a trunk is seized for applying a busy potential to every idle trunk viav their busy test circuits to make the idle trunks busy, means for releasing the seized trunk comprising a release circuit paming over the busy test circuit, and means for preventing the said lastpotential applying means from applying a potential to the busy test circuits of any other trunk that is busy at the time of said seizure whereby interference with the release is prevented.

56. In a telephon system. a plurality of trunks each comprising a main circuit and a busy test circuit. means for seizing any one of said trunks and for making the seized trunk busy. means operable when a trunk is seized for applying a busy potential to every idle trunk via their busy test circuits to make the idle trunks busy. means for releasing th seized trunk comprising a re lease circuit passing over the busy test circuit. means for preventing the said last potential applying means from applying a potential to the busy test circuits; of any other trunk that is busy at the time of said seizure whereby interference with the release is prevented. and means for extending the main circuit before the release and for rendering the first said idle trunks non-busy when the extension is made.

57. In a telephone system. a plurality of trunks each comprising a main circuit and a busy test circuit. automatic means for seizing any one of said trunks and for making the seized trunk busy. automatic means operable when a trunk is seized for applying a busy potential to every idle trimk via their busy test circuits to make the idle trunks busy. automatic means for releasing the seized trunk comprising a release circuit passing over the busytest circuit. and automatic means for preventing the said last potential applying means from applying a potential to the busy test circuits of any other trunk that is busy at the time of said seizure whereby interference with the release is prevented.

58. In a telephone system. a plurality of trunks each comprising a main circuit and a busy test circuit. automatic means for seizing any one of said trunks rod for making the seized trunk busy. automatic means operable when a trunk is wized for applying a busy potential to every idle trunk via their busy test circuits to make the idle trunks busy. automatic means for releasing the seized trunk comprising a release circuit passing over the busy test circuit. automatic means for preventing the said last potential applying means from applying a potential to the busy test circuits of any other trunk that is busy at the time of said seizure whereby interference with the release is prevented. and manual means for extending the main circuit before the release and for rendering the first said idle trunks non-busy when the extension made.

59. In a telephone system. a plurality of trunks each comprising a main circuit and a busy test circuit. means for seizing any one of said trunks: and for making the seized trunk busy. means operable when a trunk is seized for applying a busy potential to every idle trunk via their busy test circuits to make the idle, trunks busy. means for releasing the seized trunk comprising a release circuit passing over the busy test circuit. and slowacting means for preventing the said last potential applying means from applying a potential to the busy test circuits of any other trunk that is busy at the time of said seizure whereby interference with the release is prevented.

60. In a telephone system. a plurality of trunks each comprising a main circuit and a busy test circuit. means for seizing any one of said trunks and for making the seized trunk busy. means operable when a trunk is seized for applying a busy potential to every idle trunk via their busy test circuits to make the idle trunks busy. means for releasing the seized trunk comprising a release circuit passing over the busy test circuit. slowacting means for preventing the said last potential applying means from applying a otential to the busy test circuits of any ot-ier trunk that is busy at the time of said seizure whereby interference with the release is prevented. and means for extending the main circuit before the release and for-rendering the first said idle trunks non-busy when the extension is made.

61. In a telephone system. a plurality of trunks each comprising a main circuit and a busy test circuit. automatic means for seizing any one of said trunks and for making the seized trunk busy. automatic means operable when a trunk is seized for applying a busy potential to every idle trunk via their busy testcircuits to make the idle trunks busy. automatic means for releasing the seized trunk comprising a release circuit passing over the busy test circuit. and slow acting means for preventing the said last potential applying means from applying a potential to the busy test circuits of any other trunk that is busy at the time of said seizure whereby interference with the release is prevented.

62. In a telephone system. a plurality of trunks each comprising a main circuit and abusy test circuit. automatic means for seizing any one of said trunks and for making the seized trunk busy. automatic means operable when a trunk is seized for applying a busy potential to every idle trunk via their busy test circuits to make the idle trunks busy, automatic means for releasing the seized trunk comprislng a release circuit passing over the busy test circuit, slow-acting means for preventing the said last potential applying means from applying a potential to the busy test circuits of any other and trunk that is busy at the time of said seizure whereby interference with the release is prevented, and manual meansfor extending the main circuit before the release and for rendering the first said idle trunks non-busy when the extension is made.

63. In a telephone system, a plurality of trunks, means for seizing any one of said trunks, means for extending a connection from the seized trunk, means controlled from the seized trunk for rendering inoperative the said second means associated with another trunk, means for again extending connection from the seized trunk and for then restoring the means rendered inoperative to operative condition, said third means also controlled from the seized trunk to automatically extend a connection from the other trunk.

64. In a telephone system, a plurality of trunks, means for seizin any one of said trunks, means for exten ing a connection from the seized trunk, means controlled from the seized trunk for preventing the maintenance of an extension from another one of said trunks, and means for again extending connection from the seized trunk and for then restoring the third means to operative condition and for controlling said third means from the seized trunk to automatically extend a connection from the other trunk.

65. In a telephone system, a plurality of lines, a common battery, means for sending current from said battery over said lines, a plurality of trunks, an operators head set an operators position, aline extending beyond the operators position, automatic means including a plural ty of pro essively movable trunking switches contro led by a common master switch mechanism for extendin connection from one of said first lines w en a subscriber calls to a trunk line and from the trunk line to the operators head set responsive to the first establishment of current in the calling subscribers line, and means for making said operators head set inaccessible to the remaining trunk lines; operator controlled means for extending connection from the connected trunk to the line beyond and for then automatically extending a connection from another trunk line to the opemtors head set.

66. In a telephone system, a plurality of trunks each comprising a main circuit and a busy test circuit, means including a plurality of progressively movable trunking switches controlled by a common master to form an extended talking switch mechanism for seizing any one of said trunks and for busy, means operable when a trunk is seized for making every the'seizure is made via their busy test circuits, means'for extending the main circuit and for rendering said other trunks non busy when'the circuit is extended and means for releasing the seized trunk comprising a release circuit passing over the busy test circuit.

67. In a telephone system, a plurality of lines, a common battery, means-for sending current from said battery over said lines, a plurality of trunks each comprising a main circuit and a busy test circuit. means including a plurality of progressiiely mova'ble trunking switches controlled .by a common master switch mechanism for seizing any one of said trunks for one of said lines calling line and the said main circuit, means for making said seized trunk busy, means operable when a trunk is seized for making every other trunk busy as a result, via their busy test circuits, all as a result of the first establishment. of current in the calling line, means for extending the main circuit and for rendering the said other trunks nonbusy when the circuit is extended and means for releasing the seized trunk comprising a release circuit passing over the busy test circuit.

68. In a telephone system, a plurality of trunks each. comprising a main circuit and a busy test circuit, automatic means including a plurality of progressively movable trunking switches controlled by a common master switch mechanism for seizing any one of said trunks and for making the seized trunk busy, automatic means operable when a trunk is seizedfor making every othertrunk busy when the seizure is made via their busy testcircuits, manual means for extending the main circuitQautomatic means for rendering said other trunks non-busy when the circuit is extended and automatic means for releasing the seized trunk comprising a release circuit passing over the busy test circult.

69. In a telephone system, a plurality of lines, a common battery, automatic means for sending current from said battery over said lines, a plurality of trunks each comprising a main circuit and a busy test circuit, automatic means including a plurality of progressively movable trunkin switches controlled by a common master swltch mechanism for seizing any one of said trunks for one of said lines to form an extended talking circuit of the calling line and the said main circuit, automatic means for making said seized trunk busy, automatic means operable when a trunk is seized for making every other trunk busy as a result, via their busy making the seized trunk.

ther trunk busy, when circuit of the test circuits. all as a result of the first es t-ablishment of current in the calling line. manual means for extending the main circuit, automatic means for rendering the said other trunks non-busy when the circuit is extended and automatic means for releasing the seized trunk comprising a release circuit. passing over the busy test circuit.

70. In a telephone system. a plurality of trunks each comprising a main circuit and a busy test circuit. automatic means for seizing any one of said trunks and for making the seized trunk busy; another group of trunks each comprising a main circuit and a busy test circuit. automatic means for seizing any one of the trunks in said second group and for making the trunk busy when seized: automatic means operable when a trunk is seized for making every other trunk in either group busy when a seizure is made via their busy test circuits. manual means for extending the main circuit. automatic means for rendering the said other trunks non-busy when the circuit is extended and automatic. means for releasing the seized trunk comprising a release circuit closed durin conversation passing over the busy test circuit.

T1. In a telephone system. a plurality of trunks each comprising a main circuit and a busy test circuit. an auxiliary circuit and connect-ing means for each trunk for connecting the trunk with the auxiliary circuit. means for seizing any one of said trunks and for making the seized trunk busy. means operable when a trunk is seized for making every other idle trunk busy as a result of the seizure. means for operatin the said connecting means of the seized trunk to connect the seized trunk to the auxiliary c-ircuit. means for making the connecting means of the other trunks inoperative. means for extending the main circuit. for rendering the other trunks non-busy when the circuit is extended. and for automatically disconnecting from the auxiliary circuit.

T2. In a telephone system. a plurality of trunks each comprising a main circuit and a busy test circuit. an auxiliary circuit and connecting means for each trunk for connecting the trunk with the auxiliary circuit. means for seizing any one of .said trunks and for making the seized trunk busy. means operable when a trunk is seized for making every other idle trunk busy as a result of the seizure. means for operating the said connecting means of the seized trunk to connect the seized trunk to the auxiliary circuit. means for makingthe connecting means of the other trunks inoperative. means for extending the main circuit. for rendering the other trunks non-busy when the circuit is extended. and for automatically disconnecting from the auxiliary circuit and means for releasing the seized trunk comprising a release circuit passing over the busy test circuit.

T3. In a telephone system. aplurality of trunks eacn comprising a main circuit and a busy test circuit, an auxiliary circuit and connecting means for each trunk for connecting the trunk with the auxiliary circuit. automatic means for seizing any one of said trunks and for making the seized trunk busy. automatic means operable when a trunk is seized for making every other idle trunk busy as a result of the seizure. automatic means for operating the said connecting means of the seized trunk to connect the seized trunk to the auxiliary circuit. automatic means for makin the connecting means of the other trunks inoperative. manual means for extending the main circuit, and automatic means for rendering the said other trunks non-busy and for automatically disconnecting from the auxiliary circuit when the circuit is extended.

T4. In a telephone system. a plurality of trunks each. comprising a main circuit and a busy test circuit. an auxiliary circuit and connecting means for each trunk for connecting the trunk with the auxiliary circuit. automatic means for seizing any one of said trunks and for making the seized trunk busy. automatic means operable when a trunk is seized for making every other idle trunk busy as a result of the seizure. automatic means for operating the said connecting means of the seized trunk to connect the seized trunk to the auxiliary circuit. automatic means for making the connecting means of the other trunks inoperative automatic means for releasing the seized trunk comprising a release circuit passing over the busy test circuit. manual means for extending the main circuit. and automatic means for rendering the said other trunks nonbusy and for automatically disconnecting from the auxiliary circuit when the circuit is extended.

7-"). In a telephone system. a plurality of trunks each comprising a main circuit and a busy test circuit. automatic means for seizing any one of said trunks and for making the seizedjrunk busy. automatic means operable when a trunk is seized for applying a busy potential to every other trunk via their busy test circuits to make the idle trunks busy. automatic means for releasing the seized trunk comprising a release circuit passing over the busy test circuit. automatic means for preventing the said last potential applying means from applying a potential to the busy test circuits of any other trunk that is busy at the time of said seizure whereby interference with the release is prevented. manual means for extending the main circuit, and automatic means for rendering the said other trunks non-busy and for automatically disconnecting from the auxiliary circuit when the. circuit is extended.

76. In a telephone system, a plurality of lines, a plurality of stations on some of said lines, means whereby one station may signal any other stat-ion comprising a cord circuit and a plurality of ringing generators associated with the said cord, a generator circuit, a key for each generator for connecting its generator with the generator circuit, a relay common. to said keys and an energizing circuit for said relay whenever any key is operated to connect a generator with the generator circuit, means controlled by said relay to connect the generator circuit with the talking circuit for signaling the called station, a locking circuit for said relay controlled by an auxiliary relay, a circuit for the auxiliary relay, means for closing said circuit to energize said auxiliary relay before the called subscriber answers when the cord is connected with the called line, and means for breaking the said locking circuitwhen a called subscriber answers to cut off the ringing current.

77. A telephone exchange system comprising telephone lines, link circuits for interconnecting the lines, an operators telephone set, a listening relay for each link circuit operating upon connection thereof with a telephone line to connect therewith the op erators telephone set, and a second relay operated to disable all other listening relays while one of said listening relays is operated.

78. A telephone exchange system comprising telephone lines, link circuits for interconnecting the lines, an operators telephone set, a switching device for each link circuit operatlng upon connection thereof with a line to connect the operators telephone set therewith, a switching mechanism operating to disable all other switching devices while one switching device is actuated, and switching means operating upon connection of the link circuit in use with another line to restore the switching device thereof and the switching mechanism to normal position.

79. In a telephone exchange system; a plurality of subscribers lines; a plural ity of link circuits for interconnecting said lines; an operators telephone set; first relays for each of said link circuits for in cluding said op'erators telephone set therewith when. the answering end of a link cir cuit is connected with one of said subscribers lines; a second relay for disconnecting said operators telephone set from said link circuit when the calling end of the link circuit is connected with another subscribers line; and a third relay for preventing the operation of more than. one of said first relays at the same time.

S0. A telephone exchange system comprising telephone lines, link circuits for interconnecting the lines, an operators telephone set, a listening relay for each link circuit op erating upon connection thereof with a telephone line to connect the operators telephone set therewith, a second relay operated to disable all other listening relays while one of said listening relays is operated, and electromagnetic mechanism operating upon connection of the link circuit in use with another telephone line to release both the listening relay thereof and the second relay.

Signed by me at Chicago, Cook county, Illinois, this 12th day of November 1914.

TALBOT G. MARTIN.

Witnesses HERBERT W. KRACKE, GEORGE YANOCHOWSKI. 

